Re: [RFC] Multi-path IO in 2.5/2.6 ?

[James Bottomley <James.Bottomley@steeleye.com>]

Lars Marowsky-Bree <lmb@suse.de> said:
> So, what is the take on "multi-path IO" (in particular, storage) in
> 2.5/2.6?

I've already made my views on this fairly clear (at least from the SCSI stack 
standpoint):

- multi-path inside the low level drivers (like qla2x00) is wrong
- multi-path inside the SCSI mid-layer is probably wrong
- from the generic block layer on up, I hold no specific preferences

That being said, I'm not particularly happy to have the multi-path solution 
tied to a specific raid driver; I'd much rather it were in something generic 
that could be made use of by all raid drivers (and yes, I do see the LVM2 
device mapper as more hopeful than md in this regard).

> I am looking at what to do for 2.5. I have considered porting the
> small changes from 2.4 to md 2.5. The LVM1 changes are probably and
> out gone, as LVM1 doesn't work still.

Well, neither of the people most involved in the development (that's Neil 
Brown for md in general and Ingo Molnar for the multi-path enhancements) made 
any comments---see if you can elicit some feedback from either of them.

James